Nexus 5 is a fantastic device, the owners of the device has a good news from Cyanogenmod. You can update Nexus 5 to Android 4.4.4 CM11 M8 KitKat custom firmware using this simple firmware update guide. The firmware is not a official firmware by Google or LG, means you need to custom recovery like ClockworkMod and your phone to be rooted in order to flash the ROM and Google Apps package files.
- First backup all your contacts, call logs and SMS.
- Enable USB debugging mode from Settings->Applications->Development->USB debugging in your device.
- Install latest LG Nexus 5 USB drives on your computer.
Installation guide of Android 4.4.4 CM11 M8 KitKat Custom ROM on Nexus 5
2.Connect your device to computer and transfer the downloaded files to your internal SD card and make sure the files are in the SD card root.
3.Disconnect device from PC and turn off the device.
4.Now enter into bootloader mode by pressing and holding volume up+volume down and power buttons together.
5.Now enter into bootloader and go to recovery option. Here perform a full data wipe by selecting “wipe data/factory reset”, cache wipe by selecting “wipe cache partition” and also wipe dalvik cache .
6.Now go to main screen and select “install zip from SD card”. Navigate using volume keys and select Android 4.4.4 ROM zip file that you copied to your SD card and select it using the Power button.
7.Same procedure (step 6 only) is applied for Google Apps package also.
8.After installations go back and reboot the device.
For the confirmation go to Settings>>About phone to verify the firmware update.